5867. West bank of Yukon River 6 miles above mouth of Seventymile River (Calico Bluff). Collector, A. J. Collier.

2AC56. South bank of Yukon River 2 miles above mouth of Seventymile River. Pebble in conglomerate. Collector, A. J. Collier.

2645. North bank of Yukon River about 5 miles above Seventymile River. Collector, Arthur Hollick.

2646. West bank of Yukon River just above mouth of Sheep Creek (Tatonduk River). Collector, Arthur Hollick.

2647. Calico Bluff, Yukon River. Collector, Arthur Hollick.

2644, 2644A, and 2644B. Calico Bluff, Yukon River.

Collector, A. H. Brooks.

2651 and 2651A. North bank of Yukon River above island near Star.

(Star

is an abandoned settlement at the mouth of Seventymile River.) Collector, A. H. Brooks.

843. Calico Bluff, Yukon River. Collector, E. M. Kindle.

845. North bank of Yukon River 1 mile above Seventymile River. Collector, E. M. Kindle.

1796, 1796A, and 1796B. North end of Calico Bluff, Yukon River. Collector, Eliot Blackweider.

1797, 1797A, 1797B, 1797C, 1797D, 1797E, and 1797F. North bank of Yukon River at big bend north of Calico Bluff. Collector, Eliot Blackwelder.

1798 and 1798A. Calico Bluff formation, southwest of mouth of Sheep Creek, (Tatonduk River). Collector, Eliot Blackwelder.

5279. North bank of Yukon River nearly opposite Seventymile River. Collector, G. H. Girty.

5302. South end of Calico Bluff, Yukon River. Collector, G. H. Girty. 5302A. Base of Calico Bluff, Yukon River. Float specimens. Collector, G. H. Girty.

5303. North end of Calico Bluff, Yukon River. Collector, G. H. Girty. 5304. West bank of Yukon River opposite mouth of Sheep Creek (Tatonduk River). Collector, G. H. Girty.

5843 and 5843A. Calico Bluff, Yukon River. Just below base of zone B. Collector, J. B. Mertie, jr.

From

5843B. Calico Bluff, Yukon River. Zone C. Collector, J. B. Mertie, jr. 5843C. Calico Bluff, Yukon River. 4-foot bed of limestone that lies 41 feet stratigraphically above top of zone C. Collector, J. B. Mertie, jr. 5843D. Calico Bluff, Yukon River. In the 215-foot zone (see section, p. 97) about 450 feet vertically above river. Collector, J. B. Mertie, jr.

5843E. Calico Bluff, Yukon River. Float specimens. Collector, J. B. Mertie, jr.

It will be seen from the faunal list above given that 117 genera have been identified, and it is likely that 250 or more species are represented. Girty's work on these collections has been of a general nature, with the purpose of determining the age of the several collections sent to him, rather than an intensive study involving complete specific identifications and the description of new species. Many new species are present in these collections, and a thorough and detailed paleontologic study of this material would probably reveal some interesting biologic data. This fauna is related more closely to the marine Asiatic faunas described by Tschernyschew than to the Mississippian faunas of the Rocky Mountain region, and this fact,

62744 308

together with the presence of many new species, has deterred Girty from correlating it very closely with the sections of the States. Girty believes the Calico Bluff formation to be of upper Mississippian age, though not necessarily correlative with the latest Mississippian rocks. Roughly the Calico Bluff formation can be correlated with the Chester group of the United States.

Mississippian rocks, like those of the Middle Devonian series, are widespread in Alaska. One of the most persistent zones of such rocks is found along the north slope of the Brooks Range, in Arctic Alaska, where an upper Mississippian group of rocks, known as the Lisburne limestone, extends from Cape Lisburne on the Arctic Ocean. eastward almost if not quite continuously for a distance of 600 miles to the international boundary. This formation is composed of limestone and chert, and although lithologically it differs from the Calico Bluff formation, paleontologically it is very closely correlative. Stratigraphically below the Lisburne limestone in northern Alaska lies the Noatak formation, which is also known to be of Mississippian age, though not necessarily upper Mississippian. The Noatak formation is related more closely in age to the chert formation of the Yukon and to the Circle volcanics and Rampart group than to the Calico Bluff formation.

North of the Yukon, along the international boundary, Cairnes 63 collected a fauna similar to that of the Calico Bluff formation but did not differentiate the containing rocks as a separate formation. This fauna is presented in this paper in the discussion of the undifferentiated Paleozoic rocks. By plotting the localities of Cairnes's fossils, however, it appears that many of the upper Mississippian localities fall in his “shale-chert " group, of Ordovician to Carboniferous age, here mapped as undifferentiated Paleozoic, which lies just east of the boundary, between the Tatonduk River and Hard Luck Creek, and especially near to Hard Luck Creek. Hence it seems certain that the Calico Bluff formation reappears along the boundary some 15 miles northeast of its type locality at Calico Bluff.

Mississippian rocks are also known at the head of the White River and in the York district of Seward Peninsula. South of the Alaska Range another great series of basic volcanic rocks of greenstone habit, known as the Strelna formation, of Mississippian age, has an extensive development in the valley of the Chitina River. This formation, however, contains a larger proportion of interbedded sediments than the Rampart group. The Strelna formation is believed by the writer to continue southeastward into southeastern Alaska, and certain of the volcanic rocks of Lynn Canal are believed to represent this horizon. Farther southeast, in southeastern Alaska, a large representation of

68 Cairnes, D. D., The Yukon-Alaska international boundary between Porcupine and Yukon Rivers: Canada Geol. Survey Mem. 67, pp. 93-103, 1914.